For forum threads with more than 20 posts, this means you never get to see the most recent post.

Surely the RSS feed should be sorted by most recent?

Our Forums are powered by Lithium Technologies. I spoke with their support regarding this issue and unfortunately the RSS feed is designed in this way and there are no settings to change the sorting. All RSS feeds will be sorted by oldest first. Lithium support suggested posting an upgrade request on their online community.